The Baltimore County Council has approved a $1.15 billion budget for next year that includes a rise in the piggyback income tax rate, to 55 percent from 50 percent, but no change in the property tax rate.

As part of a deal with County Executive Roger B. Hayden, the council also cut $7.2 million from the executive's proposed budget. And Mr. Hayden agreed to reallocate the money to hire (( 40 new police recruits, restore cuts in the Fire Department's emergency medical services program and buy $1 million worth of computers for schools. The remainder of the money, $4.5 million, is to be added to the county's $5.5 million "rainy day fund," which was created to guard against state budget cuts this fall.

The council overwhelmingly supported the plan yesterday. Only Dundalk Councilman Donald C. Mason, D-7th, voted against the piggyback increase. Mr. Mason, and the four other freshmen council members, were elected in 1990 on a wave of voter anger about rising property taxes and increased government spending.

Council Chairman William A. Howard IV, R-6th, who strongly espoused the tax-cutter philosophy during the campaign, said the immediate criticism over the council's decision to raise taxes will be great.

But Councilman Mason disputed that. The budget agreement represents the first time the County Council has reallocated potential budget cuts to add money for county spending, rather than cutting spending to reduce taxes.